Equipment of this general type is used in particular to cut sheet metal, for instance in the can manufacturing industry, although it can also be used for cutting paper and cardboard. Cutting can bodies requires extreme accuracy and cleanliness while keeping constant high outputs.
French patent document 612,303 (Marinori) discloses a paper-cutting machine with two shafts mounted in a fixed frame, individual circular blades being displaceably affixed to the shafts.
French patent document 2,340,170 (Metal Box Ltd) describes a sheet metal cutter with a series of circular blades displaceably mounted on two separate shafts.
The two above mentioned apparatuses of the state of the art share the design of mounting the circular blades on two mutually parallel and long shafts, the adjustment of the cutting width being implemented by axially displacing the individual circular blades. It follows that each of the cooperating pairs of circular blades must be individually adjusted on the upper and on the lower shafts and then be aligned again. Obviously such a procedure is both complex and time-consuming and, moreover, may lead to inaccuracies while there always is the danger of damage to the blades. As a rule the individual circular blades are adjusted in a hydraulic manner on the long shaft using suitable oil lines. As a result, the cutting apparatus and hence the material being cut is contaminated with oil, and this feature is highly disadvantageous when making cans.
Another drawback of equipment of the state of the art is the large size of the cutting-disk shafts which is required. In order to deliver the high pressure necessary for cutting sheet metal and because of the consequent danger of bending, especially at the center of the shaft, such a shaft must have a substantial diameter. Typically, shafts 105 mm in diameter are required to cut sheet metal. Hence, such shafts are expensive and furthermore sensitive to thermal expansion. Because the shaft diameters are large, the blade diameters also must be large, and as a result the blades evince an unfavorable, fairly shallow angle of cutting and hence generate untidy cut edges.